Expandable styrene polymer beads are well known, as are the articles which can be formed therefrom. The beads ordinarily contain a small amount of gas-producing material such as n-pentane so that the beads, when heated to the softening point, expand to form a cellular product. The expanded beads are employed, for example, as insulating sheets in residential and commercial buildings, for making drinking cups, ice chests for picknickers, and the like.
The expanded, cellular styrene polymer products thus described readily support combustion, and liberate quantities of dense, black smoke.
In the production of insulating sheets of cellular styrene polymer materials, it is customery to first produce fairly large "pillows" or bulk sections of cellular material, following which the pillows are cut to the desired shape and size. The amount of scrap which is produced can be quite large, and can range up to 15% or more of the volume of the pillow. It is time consuming and difficult to collect and reuse the scrap.
Cellular, expanded styrene polymer products have good insulating qualities, and because of their light weight are easily carried and managed. Products of this type ordinarily have bulk densities in the neighborhood of 1 lb. per cubic foot. Although attempts have been made to render products of this type fireproof, I am unaware of any of such products which have become commercially feasible. Certain of these attempts have produced cellular articles having comparatively high densities (up to 50 lbs. per cubic foot; U.S. Pat. No. 3,429,836), and the presence of exceedingly large quantities of inorganic material such as silicates in such products not only renders the products overly dense for desired commercial utility, but may reduce the insulating properties of the materials.
It would be desirable to provide a system whereby pre-expanded styrene polymer beads, or particles composed of one or more of such beads, could be rendered non-combustion-supporting and could further be easily shaped into lightweight, fire-resistant, highly insulating articles.